Coastal areas, in land-sea interaction zones, are experiencing rapid urbanization, resulting in fragmentation of coastal ecosystems. Using the megalopolis of Xiamen-Zhangzhou-Quanzhou, known as Minsanjiao region, as an example, we established an ecological land-sea network using the least-cost path (LCP) algorithm based on the geospatial data (land use and land cover, marine functional zones, sensitive habitats, and protected areas). We evaluated the integrity of the ecological network using three indicators: network circuitry (α), line to node ratio (β), and network connectivity (γ). Our results show that (1) key corridors and nodes that connected the important ecological patches in the integrated land-sea network were mainly distributed in forests, grasslands (inland), and marine protected areas, while built-up areas with intensive human activities had strong barrier effects on ecological corridors; (2) coastal ecological corridors endured great pressures from rapid urbanization due to their key roles as the ecological patches connecting the land and sea and centers for urban development; (3) the high ecological network integrity scores (α=0.86, β=2.56, γ=0.91) indicated a normal ecological network status in our study area. However, the rapid coastal urban development and other intensive human activities show early warning signals of potential ecological degradation. This research provides a new method for the land-sea integration and ecological management of coastal cities though configuring the land-sea ecological network and modeling the overall land-sea ecological security of the Minsanjiao megalopolis.